linux-kernel - [PATCH 5.14 051/100] drm/ttm: Fix a deadlock if the target BO is not idle during swap

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Message-Id: <20210924124343.150751601@linuxfoundation.org>
Date:   Fri, 24 Sep 2021 14:44:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, xinhui pan <xinhui.pan@....com>,
        Christian König <christian.koenig@....com>,
        Dave Airlie <airlied@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.14 051/100] drm/ttm: Fix a deadlock if the target BO is not idle during swap

From: xinhui pan <xinhui.pan@....com>

[ Upstream commit 70982eef4d7eebb47a3b1ef25ec1bc742f3a21cf ]

The ret value might be -EBUSY, caller will think lru lock is still
locked but actually NOT. So return -ENOSPC instead. Otherwise we hit
list corruption.

ttm_bo_cleanup_refs might fail too if BO is not idle. If we return 0,
caller(ttm_tt_populate -> ttm_global_swapout ->ttm_device_swapout) will
be stuck as we actually did not free any BO memory. This usually happens
when the fence is not signaled for a long time.

Signed-off-by: xinhui pan <xinhui.pan@....com>
Reviewed-by: Christian König <christian.koenig@....com>
Fixes: ebd59851c796 ("drm/ttm: move swapout logic around v3")
Link: https://patchwork.freedesktop.org/patch/msgid/20210907040832.1107747-1-xinhui.pan@amd.com
Signed-off-by: Christian König <christian.koenig@....com>
Signed-off-by: Dave Airlie <airlied@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 32202385073a..b47a5053eb85 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1157,9 +1157,9 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
 	}
 
 	if (bo->deleted) {
-		ttm_bo_cleanup_refs(bo, false, false, locked);
+		ret = ttm_bo_cleanup_refs(bo, false, false, locked);
 		ttm_bo_put(bo);
-		return 0;
+		return ret == -EBUSY ? -ENOSPC : ret;
 	}
 
 	ttm_bo_del_from_lru(bo);
@@ -1213,7 +1213,7 @@ out:
 	if (locked)
 		dma_resv_unlock(bo->base.resv);
 	ttm_bo_put(bo);
-	return ret;
+	return ret == -EBUSY ? -ENOSPC : ret;
 }
 
 void ttm_bo_tt_destroy(struct ttm_buffer_object *bo)
-- 
2.33.0